Mark McDonald and Josiah Humphrey were barely teenagers when they went into business together selling SEO services, deepening their voices over the phone to sound older and more authoritative. It was the beginning of a beautiful millennial partnership. Three years ago, the duo—then 19 and 20, respectively—created Appster, a development company that has created apps for Jägermeister and Coca-Cola and now has a staff of more than 100 people in three countries. “We want to be a development hub for the greatest ideas in the world,” Humphrey said. For startup client Bluedot Innovation, Appster created a geo-location payment platform accurate up to five meters from the source. Nine months later, Bluedot is valued at $7.5 million. And Appster itself is projected to hit $100 million in annual revenue in the next four years—not bad for a couple of twentysomethings.